In German Patent No. 42 31 968.4 A1, a clocked power supply circuit is described in which on the output side there is an at least intermittently active load that is independent of the electrical consumer, preferably a gas discharge lamp. The arrangement comprises contains a dc/dc converter, which is connected by way of switching elements to a dc power supply. The switching signals for the switching elements are made available by a control arrangement as a function of the load condition existing on the output side. In this known power supply circuit, only one voltage is available on the output side. If the consumer is a gas discharge lamp, then to ignite it, a much greater ignition voltage is needed in comparison to the operating voltage. In the known power supply circuitry, this voltage is applied by injection of an appropriate ignition pulse by means of a transformer to be specially provided. According to the known power supply circuit, after the ignition circuit reaches the specified voltage, it outputs an ignition pulse to the smoothing capacitor. This means that the output voltage has to be boosted to this elevated value. In this known power supply circuit, the load can be switched off and has a capacitor connected in outgoing circuit. Its stored energy is not sufficient to provide the energy required within a short time, to end the ignition process with certainty after said ignition process is introduced. Due to the load having the at least intermittently active converter load, a current is applied to it and the energy stored inductively in the secondary winding will be made available after the ignition to cover the elevated power requirement of the lamp. In accordance with the objective, the at least intermittently active converter load in this known array is active for the period following ignition, until its completion.
This is not the case in the circuit according to the present invention. Rather, here, it is not the ignition, but rather the time until ignition, which is quite significant to the operation of the intermittently active converter load.